Multimodal Semiconductive Polymer for Power Cable Extrusion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductive polymer compositions for power cables face challenges in achieving improved space charge performance and processability, leading to potential premature failure and production inefficiencies due to narrow molecular weight distribution and scorch formation during extrusion.
Innovation Solution
A semiconductive polymer composition is developed using a multimodal ethylene homo- or copolymer produced with a single-site catalyst, featuring a broad molecular weight distribution, specific density, and melt flow rate ranges, which enhances space charge properties and processability by preventing premature crosslinking and improving extrudability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a narrow molecular weight distribution polymer is used, then the space charge performance is improved, but the processability and extrudability deteriorate
Solution Approach 1:
The polymer is segmented into multiple molecular weight fractions (multimodal distribution) with different characteristics. The low molecular weight fraction improves processability and extrudability, while the high molecular weight fraction maintains space charge performance and mechanical properties. This segmentation resolves the contradiction by combining fractions with complementary properties.
Solution Approach 2:
The molecular weight distribution parameters are changed from narrow to broad (multimodal) distribution. By controlling the ratio of low and high molecular weight fractions and adjusting the MWD shape, the patent optimizes both processability (lower viscosity, better extrudability) and electrical performance (space charge characteristics) simultaneously.
2Strength
If the molecular weight is increased to improve mechanical properties, then the strength is improved, but the melt flow rate decreases and processability worsens
Solution Approach 1:
The polymer is divided into multiple molecular weight fractions. The high molecular weight fraction provides mechanical strength and structural integrity, while the low molecular weight fraction ensures adequate melt flow rate and processability. This segmentation allows both requirements to be met simultaneously.
Solution Approach 2:
The patent creates a composite polymer system with multimodal molecular weight distribution, combining fractions with different molecular weights to achieve a balance between mechanical properties (from high MW fraction) and processability (from low MW fraction), similar to how composite materials combine different materials to achieve complementary properties.
3Ease of manufacture
If the extrusion temperature is increased to improve processability, then the melt flow rate is improved, but scorch formation increases and product quality deteriorates
Solution Approach 1:
The patent changes the molecular weight distribution parameters to create a multimodal structure with low molecular weight fractions that provide adequate melt flow at lower temperatures. This allows extrusion to proceed at reduced temperatures, preventing scorch formation and maintaining product quality while still achieving good processability.
Data Source
AI summary
The invention relates to a semiconductive polymer composition for use in power cables. The composition comprises a multimodal ethylene homo- or copolymer produced in a polymerization process comprising a single site catalyst whereby the polymer composition has a density of 870 to 930 kg/m3, a MFR2 of 1 to 30 g/10 min and a Mw/Mn of less than or equal to 10.